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I've been hearing about Halley's comet for a while now, and I'm just curious as to when and where to see it, and for how long. :)

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    $\begingroup$ I believe it's due back in 2061. So stay healthy. If I'm alive I'll be nearly 100, so the odds do not favor me seeing it. Traditionally it is associated with bad things happening, so there is sort of up-side to that. Sort of. :-) $\endgroup$ – StephenG Jan 24 '18 at 19:40
  • $\begingroup$ oh, that's quite interesting! :D $\endgroup$ – Eevee Jan 24 '18 at 19:41
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    $\begingroup$ @StephenG Samuel Langhorne Clemens wasn't so bad! :-) $\endgroup$ – uhoh Jan 25 '18 at 10:48
  • $\begingroup$ @StephenG So I't will be a while until we see it again $\endgroup$ – Eevee Feb 2 '18 at 19:46
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Halley's comet orbits the sun and its orbit lasts 75 years. The orbit is a long elliptical orbit. For most of those 75 years it is a cold black dot, and frozen solid in the outer solar system. But a short period during that orbit it gets close to the sun. The ice and gas begin to boil of its surface and gets blown back by the solar wind of the sun. It then starts to look like a comet.

The last time Halley's comet was close to the sun was in 1986, and so the next time will be in 2061. You won't be able to see Halley's comet until then.

enter image description here (image from University of Wisconsin)

I remember 1986, and the comet was visible but hard to see. It was a very dim fuzzy dot, that was just about visible in my binoculars. This is because, unfortunately, the Earth was a long way from the comet. In 2061 Earth will be even further from the comet, however Earth will be better positioned when Halley is closest to the sun, so it should make a good show, and be clearly visible to the naked eye. Comet predictions are hard as much depends on exactly how much water vapour boils off, and this is hard to predict. Comets can have sudden changes in activity.

Moreover, Halley's comet isn't the only comet. There are others that can be as visible as Halley will be in 2061. There are also long period comets that are undiscovered until they come close to the sun. These can be very bright. Comet Hale-Bopp was a "great" comet in 1997 and was visible for many months. Another great comet could come along any time but we can't predict when.

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    $\begingroup$ You say 2061 will be even worse than 1963, but Wikipedia says It is expected to have an apparent magnitude of −0.3, compared with only +2.1 for the 1986 apparition (Source). Is Wikipedia wrong? Its source does not contain information related to the claim (it may have before). $\endgroup$ – gerrit Jan 24 '18 at 21:26
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    $\begingroup$ ... I may be wrong, I was writing from memory. Consider it [citation needed] until I get around to checking it. $\endgroup$ – James K Jan 24 '18 at 22:20
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    $\begingroup$ @gerrit +2.1 doesn't help if it's close to the Sun for example and you're on Earth's surface looking through the blue sky. Of course in 2061 things may be different. $\endgroup$ – uhoh Jan 25 '18 at 10:52
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    $\begingroup$ I wonder when we'll first be able to see Comet Halley with optical aid or radio waves or whatever. As our technology improves, it might be a lot sooner than 2061, especially after the comet turns around in 2024. $\endgroup$ – barrycarter Jan 25 '18 at 15:48
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    $\begingroup$ We can see it now, if we look hard enough. It was imaged in 2003, as practice for identifying TNO. The distance hasn't increased much since then. It would have a magnitude of about 28-29, but it can now be seen even at aphelion. $\endgroup$ – James K Jan 25 '18 at 17:00

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